Hybrid vehicles potentially offer improvements to fuel efficiency and vehicle driving range over non-hybrid vehicles. However, a hybrid vehicle may not operate in a similar manner when engaged in different driveline configurations. Further, control commands and responses may not have a desired response if they are simply carried over from two wheel or four wheel drive high gear modes to four wheel drive low gear mode. For example, if a stopped engine is restarted while a vehicle is in a four wheel drive low gear range in the same manner as the vehicle is started while in a two wheel drive mode, the vehicle may not launch in a manner that is consistent with launching the vehicle in two wheel drive mode.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method of adjusting operation of a hybrid vehicle, comprising: automatically restarting an engine in response to a first condition while the hybrid vehicle is operating in a four wheel drive low gear range; and automatically restarting the engine in response to a second condition other than the first condition while the hybrid vehicle is not operating in the four wheel drive low gear range.
By accounting for the driveline operating mode, it may be possible to improve vehicle launch in different driveline operating modes. For example, it may be more desirable to launch a vehicle with an engine and an electric machine while the vehicle is operated in some driveline modes. On the other hand, it may be desirable to launch the vehicle solely via the electrical machine while the vehicle is operated in other driveline modes. Launching the vehicle solely via the electric machine may provide a smoother launch in some driveline modes. Conversely, launching the vehicle with the engine and electric machine may improve launch smoothness in other driveline modes.
The present description may provide several advantages. Specifically, the approach may improve vehicle launch in different driveline modes. Further, the approach may improve vehicle drivability. Further still, the approach may reduce driveline wear, thereby increasing the operating life of the driveline.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.